PC:
Project Reality has become my favorite game/mod now, it's as close to the gameplay/depth of T1/T2 that I've found in a bullet shooter. Awesome team game. Great maps. buggy for some, new patch & maps coming any day
Legions - once or twice a week
CoD4 - Once every few weeks
I try lots of alphas and betas when I can but nothing thats hooked me.
XBox360 - Nothing lately